Re: [PATCH 2/2] configs: Add generic qcom_tfa_optee_defconfig

Neil Armstrong
2026-01-15T13:35:31Z

On 1/15/26 14:27, Sumit Garg wrote:
> On Thu, Jan 15, 2026 at 02:03:29PM +0100, Neil Armstrong wrote:
>> On 1/15/26 13:25, Sumit Garg wrote:
>>> + Jens (OP-TEE driver author in U-Boot)
>>>
>>> On Thu, Jan 15, 2026 at 11:49:49AM +0100, neil.armstrong@linaro.org wrote:
>>>> On 1/15/26 07:10, Sumit Garg wrote:
>>>>> On Wed, Jan 14, 2026 at 03:56:02PM +0100, Casey Connolly wrote:
>>>>>>
>>>>>>
>>>>>> On 09/01/2026 12:02, Sumit Garg wrote:
>>>>>>> On Thu, Jan 08, 2026 at 05:41:42PM +0100, Casey Connolly wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On 29/12/2025 12:43, Sumit Garg wrote:
>>>>>>>>> From: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>>>>>>
>>>>>>>>> Recently upstream TF-A/OP-TEE has started gaining support for Qcom
>>>>>>>>> platforms. RB3Gen2 being the first one and more to come. U-Boot in
>>>>>>>>> corresponding boot flow is packaged as a position independent executable.
>>>>>>>>>
>>>>>>>>> So, lets add a generic U-Boot defconfig for Qcom platforms to support
>>>>>>>>> TF-A/OP-TEE based TrustZone stack. Build command:
>>>>>>>>>
>>>>>>>>> $ make qcom_tfa_optee_defconfig
>>>>>>>>> $ make -j`nproc` DEVICE_TREE=qcom/qcs6490-rb3gen2
>>>>>>>>
>>>>>>>> This would be better suited as a config fragment rather than a new
>>>>>>>> defconfig imo.
>>>>>>>
>>>>>>> That's fine with me to add it as a config fragment.
>>>>>>>
>>>>>>>>
>>>>>>>> But more importantly, enabling OPTEE support in U-Boot doesn't imply
>>>>>>>> that it will be used, just that it's supported.
>>>>>>>
>>>>>>> There are real use-cases of OP-TEE in U-Boot for Qcom platforms like
>>>>>>> secure EFI variables based on OP-TEE secure storage. Have a look here [1].
>>>>>>>
>>>>>>> And sure there will be more such use-cases like fTPM, KASLR etc. can be
>>>>>>> supported based on OP-TEE.
>>>>>>
>>>>>> I was referring literally to the fact that CONFIG_OPTEE being enabled
>>>>>> doesn't imply that OP-TEE is running, it's faulty logic to assume that's
>>>>>> the case and add nodes to the DT.
>>>>>
>>>>> I don't disagree here as having a runtime check is always a better
>>>>> choice then a compile time config option. However, there isn't a common
>>>>> info method from properietary firmware that says if QTEE is running
>>>>> instead of OP-TEE.
>>>>>
>>>>>>
>>>>>> I just checked and there is an SMC call that tells you the UUID for the
>>>>>> trusted OS, referred to as OPTEE_SMC_CALL_GET_OS_UUID in U-Boot and
>>>>>> OPTEE_ABI_CALL_GET_OS_UUID in OP-TEE. Presumably this identifies OP-TEE
>>>>>> specifically.
>>>>>
>>>>> Also, we don't know how the QTEE will react to this OP-TEE specific SMC
>>>>> call given it's different variants running on legacy and the newer SoCs.
>>>>> So I would suggest to better gate OP-TEE presence behind a compile time
>>>>> check only.
>>>>
>>>> So you say it's fine to add the optee node, and the driver will bail out if
>>>> OPTEE is not present, but it's not good to call OPTEE_SMC_CALL_GET_OS_UUID
>>>> in the fixup code to enable OPTEE only if present ?
>>>>
>>>> It's literally the same, my point in https://lore.kernel.org/all/b60d5ee7-fa27-4dc1-8a09-964912ec5654@linaro.org/
>>>> was exactly that, just call OPTEE_SMC_CALL_GET_OS_UUID and add the OPTEE
>>>> node only if present _AND_ if CONFIG_OPTEE is enabled.
>>>>
>>>> Move the CONFIG_OPTEE enable in a fragment and we're done, you will only
>>>> select OPTEE explicitly on desired platforms, and won't run the naughty
>>>> OPTEE_SMC_CALL_GET_OS_UUID on old crappy platforms.
>>>
>>> I am still trying to understand what benefit does invoking
>>> OPTEE_SMC_CALL_GET_OS_UUID from platform code provides us. Surely it
>>> can't be used to detect OP-TEE not present when QTEE is running due to
>>> unknown behaviour with QTEE.
>>
>> Sorry but what exactly do you expect that will happen if you enable the OPTEE
>> driver when running with QTEE ?
>
> The OP-TEE SMC calls are not at all supported with QTEE, so the expected
> behaviour is undefined. IOW, the OP-TEE SMC ABI is not compatible with
> QTEE. However, it's going to be hit and trial method to see what QTEE
> responds to OP-TEE SMC calls. So it's not a reliable source of
> information we can use to detect which TEE is present or not.

So until we know, this change is a no go, we can't just add the /optee node
and hope the person building uboot did the right thing.

I propose an alternate way, is to check for QTEE and then test for OPTEE.

Neil

>
> -Sumit
>
>>
>>>
>>> Jens,
>>>
>>> Will it be fine with you to expose is_optee_api() from the OP-TEE driver
>>> for the platform code to invoke it independently? Just for the sake of this
>>> discussion in case people still insist on it being the right thing to do.
>>>
>>> -Sumit
>>>
>>>>
>>>> Neil
>>>>
>>>>>
>>>>>>
>>>>>> My suggestion would be to make this SMC call if CONFIG_OPTEE is enabled
>>>>>> in qcom_psci_fixup(), compare the UUID and add the node if it matches.
>>>>>
>>>>> That's exactly the first SMC call that U-Boot and Linux OP-TEE driver
>>>>> does to compare the UUID here [1] and bail out of the driver. I don't
>>>>> see a value of a redundant invoke in the Qcom specific platform code.
>>>>>
>>>>> [1] drivers/tee/optee/core.c:823: if (!is_optee_api(pdata->invoke_fn))
>>>>>
>>>>> -Sumit
>>>>>
>>>>>>
>>>>>>>
>>>>>>> [1] lib/efi_loader/efi_variable_tee.c
>>>>>>>
>>>>>>>>
>>>>>>>> So I think the more appropriate patch here would be to just enable
>>>>>>>> OP-TEE in qcom_defconfig (assuming the binary size isn't significantly
>>>>>>>> affected).
>>>>>>>
>>>>>>> The OP-TEE driver in U-Boot itself is probed based on DT and it's not
>>>>>>> only specific to Qcom platforms but every other platform using OP-TEE.
>>>>>>>
>>>>>>>>
>>>>>>>> Considering the other patch is based on this assumption that if OP-TEE
>>>>>>>> support is enabled then the board must be using it, a different approach
>>>>>>>> is definitely needed.
>>>>>>>
>>>>>>> Yeah that's true even with TF-A boot flow, there is possibility to boot
>>>>>>> without OP-TEE as well. However, TF-A generally doesn't provide a
>>>>>>> generic option to detect whether OP-TEE is running or not.
>>>>>>>
>>>>>>>>
>>>>>>>> When I was looking into this last year I remember discussing this same
>>>>>>>> issue from the Linux side, there is a good argument to be made that
>>>>>>>> OP-TEE support in Linux shouldn't be based on the devicetree -
>>>>>>>> particularly in the Qualcomm case where whether or not OP-TEE is used is
>>>>>>>> a simple software change, nothing to do with hardware.
>>>>>>>
>>>>>>> Sadly it's true for every other silicon vendor too. But OP-TEE support
>>>>>>> based on DT has become an ABI unless migration for OP-TEE support based
>>>>>>> on FF-A comes into picture.
>>>>>>>
>>>>>>>>
>>>>>>>> So in general I'm not particularly keen on this approach, I think it
>>>>>>>> /might/ be acceptable for U-Boot to have some fixup code to add the
>>>>>>>> OP-TEE node if OP-TEE is in use with the idea of phasing that out in
>>>>>>>> favour of runtime detection in the OS itself. I'd also expect that fixup
>>>>>>>> code to go in the generic U-Boot DT fixup code that runs before we jump
>>>>>>>> to the OS (like the EFI DT fixup function).
>>>>>>>
>>>>>>> The EFI DT fixup code is already there based on U-Boot DT. Have a look
>>>>>>> here:
>>>>>>>
>>>>>>> boot/image-fdt.c:627: fdt_ret = optee_copy_fdt_nodes(blob);
>>>>>>>
>>>>>>> In general on Arm platforms there isn't any SMC bus to detect
>>>>>>> dynamically if there is support for OP-TEE or not. That's why
>>>>>>> platform bus was choosen for the U-Boot and Linux OP-TEE driver. It's
>>>>>>> similar to how we have the SCM DT node for Qcom platforms.
>>>>>>>
>>>>>>> FF-A bus tries to solve that problem to unify that approach for future
>>>>>>> platform but U-Boot hasn't yet gained support for FF-A based OP-TEE
>>>>>>> driver too.
>>>>>>>
>>>>>>> Anyhow, this is the sanest way I can come up with to enable OP-TEE
>>>>>>> support in a general way for all the Qcom platforms. This is aligned
>>>>>>> with how OP-TEE support is detected for other silicon vendors too.
>>>>>>>
>>>>>>> -Sumit
>>>>>>>
>>>>>>>>
>>>>>>>> Kind regards,
>>>>>>>>
>>>>>>>>>
>>>>>>>>> For more information refer here:
>>>>>>>>> https://trustedfirmware-a.readthedocs.io/en/latest/plat/qti/rb3gen2.html
>>>>>>>>>
>>>>>>>>> Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>>>>>> ---
>>>>>>>>> configs/qcom_tfa_optee_defconfig | 7 +++++++
>>>>>>>>> 1 file changed, 7 insertions(+)
>>>>>>>>> create mode 100644 configs/qcom_tfa_optee_defconfig
>>>>>>>>>
>>>>>>>>> diff --git a/configs/qcom_tfa_optee_defconfig b/configs/qcom_tfa_optee_defconfig
>>>>>>>>> new file mode 100644
>>>>>>>>> index 00000000000..c398521770f
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/configs/qcom_tfa_optee_defconfig
>>>>>>>>> @@ -0,0 +1,7 @@
>>>>>>>>> +# Configuration for building a generic U-Boot image
>>>>>>>>> +# with support for TF-A/OP-TEE based Arm TrustZone stack.
>>>>>>>>> +
>>>>>>>>> +#include "qcom_defconfig"
>>>>>>>>> +
>>>>>>>>> +CONFIG_TEE=y
>>>>>>>>> +CONFIG_OPTEE=y
>>>>>>>>
>>>>>>>> --
>>>>>>>> // Casey (she/her)
>>>>>>>>
>>>>>>
>>>>>> --
>>>>>> // Casey (she/her)
>>>>>>
>>>>
>>